The heart is a muscular pump made
up of four chambers. The two upper chambers are called
atria, and the two lower chambers are called ventricles. A natural electrical
system causes the heart muscle to contract and pump blood through the heart to
the lungs and the rest of the body.

Why It Is Done

Find the cause of unexplained chest pain or pressure, which could be caused
by a heart attack, inflammation of the sac surrounding the heart (pericarditis), or
angina.

Find the cause of symptoms of
heart disease, such as shortness of breath, dizziness, fainting, or rapid,
irregular heartbeats (palpitations).

Find out if the walls of the
heart chambers are too thick (hypertrophied).

Check how well
medicines are working and whether they are causing side effects that affect the
heart.

Check how well mechanical devices that are implanted in the
heart, such as
pacemakers, are working to control a normal
heartbeat.

Check the health of the heart when other diseases or
conditions are present, such as
high blood pressure,
high cholesterol, cigarette smoking,
diabetes, or a family history of early heart
disease.

How To Prepare

Many medicines may change the results
of this test. Be sure to tell your doctor about all the nonprescription and
prescription medicines you take. If you take heart medicines, your doctor will
tell you how to take your medicines before you have this test.

Remove all jewelry from your neck, arms, and wrists. Men are usually
bare-chested during the test. Women may often wear a bra, T-shirt, or gown. You will be given a cloth
or paper covering to use during the test.

Talk to your doctor
about any concerns you have regarding the need for the test, its risks, how it
will be done, or what the results will mean. To help you understand the
importance of this test, fill out the
medical test information form(What is a PDF document?).

You may receive an EKG as part
of a physical examination at your health professional's office or during a
series of tests at a hospital or clinic. EKG equipment is often portable, so
the test can be done almost anywhere. If you are in the hospital, your heart
may be continuously monitored by an EKG system; this process is called
telemetry.

During an EKG:

You will lie on a bed or table. Areas on your
arms, legs, and chest where small pads or patches (electrodes) will be placed are
cleaned and may be shaved to provide a clean, smooth surface to attach the
electrodes.

Several electrodes are
attached to the skin on each arm and leg and on your chest. These are hooked to a
machine that traces your heart activity onto a paper. If an older machine is
used, the electrodes may be moved at different times during the test to measure
your heart's electrical activity from different locations on your chest. After
the procedure, the electrode paste is wiped off.

You will be asked
to lie very still and breathe normally during the test. Sometimes you may be
asked to hold your breath. You should not talk during the test.

The test
usually takes 5 to 10 minutes to complete.

How It Feels

The electrodes may feel cool when they
are put on your chest. If you have a lot of hair on your chest, a small area
may need to be shaved to put the electrodes on. When the electrodes are taken
off, they may pull your skin a little.

Risks

There is no chance of problems while having an
electrocardiogram (EKG or ECG). An EKG is a completely safe test. In most
cases, there is no reason why you should not be able to get an EKG.

The electrodes are used to transfer an image of the electrical activity
of your heart to tracing on paper. No electricity passes through your body from
the machine, and there is no danger of getting an electrical shock.

Results

An electrocardiogram (EKG or ECG) is a
test that checks for problems with the electrical activity of your heart. An
EKG translates the heart's electrical activity into line tracings on paper. The spikes and dips in the line tracings are called waves.

Your doctor will look
at the pattern of spikes and dips on your electrocardiogram to check the
electrical activity in different parts of your heart. The spikes and dips are
grouped into different sections that show how your heart is working.

Electrocardiogram (EKG or ECG) results

Normal:

The heart beats in a regular rhythm, usually
between 60 and 100 beats per minute.

The tracing looks normal.

Abnormal:

The heart beats too slow (such as less than 60 beats
per minute).

The heart beats too fast (such as more than 100 beats per
minute).

The heart rhythm is not regular.

The tracing does not look
normal.

What Affects the Test

Reasons you may not be able to
have the test or why the results may not be helpful include:

Not having the electrodes securely attached to
your skin.

Moving or talking during the
test.

Exercising before the test.

Being anxious or
breathing very deeply or rapidly.

What To Think About

Sometimes your EKG may look normal even when
you have heart disease. For this reason, the EKG should always be interpreted
along with your symptoms, past health, physical examination, and, if necessary,
other test results.

An electrocardiogram cannot predict whether you
will have a
heart attack.

At first, an EKG done
during a heart attack may look normal or unchanged from a previous EKG. So the
EKG may be repeated over several hours and days (called serial EKGs) to look
for changes.

Sometimes EKG
abnormalities can be seen only during exercise or while symptoms are present.
To check for these changes in the heartbeat, an ambulatory EKG or stress EKG
may be done.

A stress EKG
is a type of EKG done during exercise. A resting EKG is always done before an
exercise EKG test, and results of the resting EKG are compared to the results
of the exercise EKG. A resting EKG may also show a heart problem that would
make an exercise EKG unsafe. To learn more, see the topic
Exercise Electrocardiogram.

Electrocardiograms are not recommended for people who are healthy and have no symptoms of heart disease.1

Sometimes doctors automatically schedule routine tests because they think that's what patients expect. But experts say routine heart tests can be a waste of time and money. To learn more, see Heart Tests: When Do You Need Them?

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